Hello Malice and Welcome to the Forum!

Great to hear of more Canadains keeping Red-Eyed Leaf Frogs, as they are getting hard to find in Canada.

The only issue with your set-up is the side mounted heat pad, you will want a bottom mounted heat pad to warm the substarte and let the heat rise, if you keep the heat pad on the side of the tank, there is a chance one of the frogs will sleep on the glass where the heat pad is, and burn it's self. Very important to move it. Other than that, great set-up!

Though I do not own Red-Eyed Leaf Frog's, I believe I may be able to help here;

Frog X sounds like a large female, and I would doubt that he/she is eating all of the crickets, a good amount to feed is 4-5 crickets per frog, every other day. Feeding this many crickets will ensure each frog is eating an adaquate amount. Something you can try is, take a small, shallow ceramic of glass bowl, and put 5-8 crickets in it, the crickets will scurry around in the bowl trying to escape, but will be unable due to not being able to aquire traction to jump on glass. I do this for most of my frogs, and they will come to the edge of the bowl and pick off the crickets one by one.

I wouldn't worry about Frog X, he/she seems like a happy, Red-Eyed Leaf Frog with a good appetite, and the difference of size between 2" STV and 2.5" is not enough to cause any sort of worry.

~Royce